There are many kinds of enzymes in the organism, including several bio-enzymes with central structure of carboxylate-bridged dinuclear iron, such as ribonucleotide reductase (RNR) and soluble methane monooxygenase (sMMO), which can catalyze some important substrates in the organisms and play a very important role. Therefore, it is a challenging work for simulating the structures and functions of these bio-enzymes and of great significance. (Acc. Chem. Res. 2011, 44, 280-288; Coord. Chem. Rev. 2013, 257, 3-26.).
Anions exist in the life body widely with very important functions. Fluoride ion is one of the trace elements indispensable to the human body. Fluorine is an indispensable part of the teeth and bones. Appropriate amount of fluoride ion can effectively prevent dental caries disease, so toothpastes contain a trace amount of fluoride ion. However, intake of a lot of fluoride ions may cause fluorosis, and diseases such as osteoporosis and urolithiasis, etc.; and if severe, it may affect children's intelligence development and physiological system. And domestic water contains a trace of fluoride ion. For its importance, the fluoride ion detection is particularly important and critical (Chem. Rev. 2014, 114, 5511-5571; Chem. Soc. Rev. 2010, 39, 3746-3771; Chem. Commun. 2009, 2809-2829.).
Methods for fluoride ion detection include electrochemical process, 19F-NMR analysis, UV analysis and fluorescence analysis. The first three methods have limitations such as expensive equipment, unable to have a real-time detection, etc., while the fluorescence analysis has the advantages of high sensitivity, real-time detection, ultra low concentration detection and intracellular detection, etc. Therefore fluorescence analysis for fluoride ion detection has attracted the attentions of researchers in recent years.
At present, the use of metal complex fluorescent probe to detect fluoride ion is rarely reported. The central metals of probes are mainly ruthenium (Ru), cobalt (Co), europium (Eu) and iron (Fe), etc., and most of the fluorophores or chromophores are phenanthroline and naphthalene, etc. (Dalton Trans. 2009, 12, 2096-2102; Dalton Trans. 2012, 41, 4484-4496; Appl. Organometal. Chem., 2008, 22, 258-261; Analyst, 2013, 138, 278-283; Polym. Chem., 2012, 3, 2640-2648.), while the fluoride ion fluorescent probes containing carboxylate-bridged binuclear iron-sulfur clusters have not been reported yet. Therefore, it has innovation and values to conduct studies on this type of fluoride fluorescent probes.